1. Field of the Invention
The invention relates to interfaces, which can be used for example in connection with operating devices for the operation of illumination means.
2. Related Technology
Illumination systems for the illumination of large complexes or buildings, in which a plurality of luminaires arranged decentrally distributed are controlled by a central control unit, require the possibility of an extensive and reliable data interchange due to the variety of functions available. Whilst with earlier illumination systems it was known solely to transmit to the various luminaires switch-on and switch-off commands from a central control unit, modern illumination systems now provide the possibility of a data transfer from the luminaires to the central control unit, to transmit for example information with regard to the current operating state as well as fault information. The luminaires or lamp operating devices provided for the operation of such an illumination system correspondingly have a communication interface which is configured not only for data reception but also is able itself to send information on a bus line system.
The recently newly developed illumination systems or lamp operating devices work predominantly according to the so-called DALI standard. This DALI (Digital Addressable Lighting Interface) standard is a new simple and user-friendly interface for the realization of intelligent and functional light management systems. An substantial feature of the DALI standard is that the control commands and information are transmitted in a digital manner and correspondingly the various devices of the system have a bidirectional digital interface.
It is required in the transmission of digital control signals for light control that the bit lengths and flank developments (steepnesses) realised by the interfaces are kept within a certain range. For example according to the DALI standard there is permitted a tolerance range of only ±10% compared with the ideal bit length of 416 μsec. Since however the interfaces being used are normally constructed as economically as possible, and particularly the transmission branch responsible for the realization of the bit lengths is configured considerably more complexly and therefore more susceptible to component tolerances than the reception time is, there arises the problem that this requirement can be adhered to only with difficulty. Particularly temperature effects and intolerances of the components can lead in the worst case to the bit length realized by the transmission branch of an interface lying outside the permitted range, which would prevent a data interchange.
Similar problems also arise with non-digital bidirectional interfaces with which the signals distributed by the transmission branch also must likewise fulfil certain requirements, which—due to the trend towards cost saving mentioned above—can be complied with only with difficulty.